The recent dispute between Level 3 Communications and Cogent Communications demonstrates why firms should use more than one ISP, says analyst Gartner.
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At the beginning of the month, Level 3 ceased its peering relationship with Cogent, claiming the connectivity arrangement was financially unfair – an allegation Cogent rejected.
The dispute initially led to thousands of internet users being cut off from other users. Faced with pressure from its customers, Level 3 relented and restored connectivity to Cogent.
Gartner said the dispute underscored the vulnerability of the internet’s connections. The internet is a network of networks, so for one ISP to reach the network of another ISP, it must either peer with that ISP or buy transit through another service provider that peers with that ISP.
When Level 3 ceased its peering relationship with Cogent, "single-homed" customers – those who buy internet connectivity from just one of these providers – could not reach customers on the other network.
Level 3 not only disrupted connectivity to Cogent’s customers, but for its own too. Multi-homed customers could still reach the other provider, via their other ISP connections, although this may have resulted in greater network latency (delays), said Gartner.
Gartner said this wasn’t the first time peering relationships had ceased, either deliberately or accidentally, and nor would it be the last.
It said no matter how many circuits firms purchase from a single ISP, or how reliable that ISP’s operations are, firms are vulnerable unless they are multi-homed.
Gartner said every location that requires mission-critical internet connectivity, including externally hosted websites, should be multi-homed.
It said firms must buy connectivity through at least two ISPs, and ensure that the second ISP is not simply a customer of the first.